- In general, embryos that achieve an evolutionary pregnancy begin their re-expansion within 50 minutes after devitrification. The embryos’ behavior during these first moments as it returns to life helps us to identify embryos with up to 30% higher chances of achieving pregnancy.
- This work provides objective quantitative values for the variables involved in blastocyst re-expansion, as opposed to the subjective morphological evaluation that has been used to date.
MALAGA, 21 APRIL 2023
Traditionally, parameters that influence embryo morphology, which can be related to its chances of implantation, have been studied. In addition, in recent years, embryo evaluations performed using a time-lapse system have provided a more precise understanding of embryo development, identifying different morphokinetic parameters as markers of embryo viability, which have served to define complementary models of embryo selection. However, after vitrification and devitrification procedures, blastocysts undergo multiple morphological changes that may make it difficult to evaluate their quality, and little is known so far about the application of this technology to vitrified and devitrified blastocysts.
This is where the study “Analysis of the morphological dynamics of blastocysts after vitrification/warming: defining new predictive variables of implantation” was created, led by Dr. Marcos Meseguer, scientific supervisor at IVI and embryologist at IVI Valencia, which is being presented today at the 10th International IVIRMA Congress.
“In our work we evaluate the post devitrification dynamics of embryos to predict the implantation potential of devitrified blastocysts using Artificial Intelligence (AI) based Artificial Neural Networks (ANN). In this sense, we are working on an AI algorithm that studies the embryo’s behavior from devitrification to transfer, which lasts about 4 hours approximately. Thus, AI shows us that an embryo that begins its expansion early (when the average expansion time is 50 minutes) and carries out this process quickly, acquiring a surface area of more than 0.14 square millimeters, can implant up to 30% more than an embryo that expands later and more slowly during those first 4 hours of life. AI also allows us to identify embryos that, despite showing good morphology, have a low probability of implanting because when they devitrify, they have either taken a long time to expand or have expanded very little,” explained Dr. Meseguer.
This is a retrospective analysis on a sample of 511 devitrified blastocysts, with the main objective of describing the variables involved in the morphological dynamics of vitrified and subsequently devitrified blastocysts during the period of time between devitrification and embryo transfer in an attempt to better understand the embryo re-expansion procedure.
“When we vitrify the embryo, we leave it in an inert state, removing the water, which is what drives all the machinery in the cell. The moment you remove the water, it is as if time stops, and the embryo can remain like this for years without time having a negative impact on its quality. When we reactivate time, we add the water back into the embryo, this process is gradual and not all embryos do it in the same way. The way the water enters and the antifreeze (which is the cryoprotectant) exits is not the same for all embryos, and not all embryos start at the same time either. And this is the starting point of our work: we have seen that embryos in which the water begins to enter earlier have a better prognosis. And embryos that expand faster will do better than those that expand more slowly. This leads us to correlate the re-expansion of devitrified blastocysts with their chances of implantation. Thus, more than 60% of the re-expanded blastocysts were successfully implanted, compared to 6% of those that were not re-expanded after devitrification,” said Dr. Meseguer.
Nowadays, prolonged embryo culture and transfer at the blastocyst stage is common practice, which has shown an improvement in embryo selection and, therefore, in the success rates of reproductive treatments. This strategy involves cryopreservation of all viable blastocysts and their transfer in subsequent cycles, thus avoiding the risk of ovarian hyperstimulation.
This growing increase in delayed transfer cycles has boosted the development of increasingly precise selection criteria to improve the outcomes of vitrified blastocyst transfers.
“It is well known that each observation involves exposure to suboptimal conditions outside the controlled environment of an incubator, which can potentially affect treatment success. Hence, continuous monitoring of devitrified blastocysts using time-lapse systems can provide us with valuable information about their implantation potential while they remain in a stable, controlled culture environment. At this point, it is important to highlight that all blastocysts were vitrified and devitrified using the Cryotop method, and they were placed in the EmbryoScope immediately after devitrification until transfer. Moreover, another differential element of our work points to the fact that it provides objective quantitative values for the variables involved in blastocyst re-expansion, as opposed to the subjective morphological evaluation that has been used for blastocyst re-expansion to date,” stated Dr. Meseguer.
We can thus conclude that Artificial Intelligence analysis of the dynamics of vitrified and devitrified blastocysts could be useful in predicting their implantation potential. Therefore, the use of predictive models in vitrified cycles could avoid the transfer of vitrified embryos with low success rates. However, the observed correlations and the proposed algorithm should be validated in a prospective trial to evaluate their efficacy.
About the 10th International IVIRMA Congress
From 20 to 22 April, the 10th International IVIRMA Congress on Assisted Reproduction will be held, attracting the main researchers worldwide in the sector. At this event we present the advances achieved in the field of Reproductive Medicine, the most innovative techniques and the results of the latest research. In addition, it is a meeting point for sharing best practices to improve the daily results in this activity. The Congress, the tenth edition of which is held this year in Malaga, brings together more than 1,200 specialists from 57 countries, and is held every two years.